The current digital still-shot cameras, and the like have an auxiliary light source for radiating auxiliary light and this is mounted on the autofocus mechanism for measuring distance or focusing. The contrast of a photographic subject can be improved and the autofocus operation can be appropriately performed, even in relatively dark places, by radiating auxiliary light onto the photographic subject with auxiliary light from the auxiliary light source.
A light emitting diode is a typical auxiliary light source (see, for example, JP (Kokai) [Unexamined Japanese Patent Publication] 2003-259,196; JP (Kokai) [Unexamined Japanese Patent Publication] 2003-319,405; and JP (Kokai) [Unexamined Japanese Patent Publication] 2003-258,307). A light emitting diode is small but capable of providing sufficient light without a flash. Consequently, it is effective as an auxiliary light source for digital cameras that must be small or other cameras mounted on a portable terminal.
By means of conventional light emitting diodes used as auxiliary light sources, the degree to which light is condensed is increased and center luminosity is also increased by providing the lens part, which is positioned overlapping the light emitting diode element, with predetermined dimensions and shape. As a result, the zoom ratio is increased and auxiliary light reaches the subject to be photographed even when photographing a subject that is relatively far away; therefore, the user can effectively use the autofocus function.
Nevertheless, when photographing a subject that is relatively close using a wide-angle lens, auxiliary light of a small directional angle does not hit near the center of the photographic range on the subject, and as a result, the distance of the subject cannot be known measured and effective autofocusing is not possible.
On the other hand, when the LED radiation range with a wide-angle lens is enlarged in order to cause some of the light to impinge near the center, it is not possible to effectively autofocus when photographing a subject that is relatively far away, as previously mentioned.
Therefore, the first object of the present invention is to provide a light emitting diode as an auxiliary light source capable of radiating auxiliary light near the center of a subject to be photographed, even with wide-angle photography of a subject that is relatively close, as well as a system for controlling the light emission of auxiliary light that is ideal for cameras that use this light emitting diode.
A second object of the present invention is therefore to provide a small auxiliary light source and a light emitting control system with which it is possible to keep energy consumptions constant and electrically turn on and off the radiation of auxiliary light onto a subject to be photographed.